Leak detection is an essential aspect of quality control in the construction of aircraft fuel tanks and the like. To check the integrity of tanks during and after construction a variety of methods are used, for example, the tank is pressurized with air and a soap film is applied to the area being inspected and the formation of bubbles is visually noted. Another method involves pressurizing the tank being tested with ammonia gas and spraying the surface being tested with a viscous liquid which contains an acid-base indicator which will change color if a tank leak allows ammonia gas to escape. Still another method of testing for leaks involves pressurizing the tank with helium gas and detecting escaping gas with a mass spectrometer. Yet another method for detecting leaks in fuel tanks uses thermographic techniques. Another method of detecting fuel leaks in both partially assembled or assembled aircraft involves applying an oil red O dyed talc to the surface being tested. The talc is applied by mixing it with 1,1,1 trichloroethane and spraying the mixture onto the surface being tested. The trichloroethane quickly evaporates leaving a pink powder on the test area. This method has been found to be an effective indicator of fuel leaks, however, the material used in the test procedure has several undesirable characteristics. The dye oil red O is a petroleum dye that is soluble in hydrocarbon solvents such as 1,1,1 trichloroethane and JP-5 jet fuel and this solubility causes some of the dye to migrate from the talc carrier into the surface of the paint used on the test area thereby staining it. Another undesirable characteristic is the similarity of the relation of the oil red O dye with water and its reaction to jet fuel. If either fuel or water contacts the oil red O impregnated talc the color of the talc changes from pink to red thus making the test meaningless if water is present as a mist, spray, or as falling rain. This characteristic of the dye decreases the usefulness of the test in the field. Other methods of detecting leaks are disclosed in U.S. Pat. Nos. 3,368,994; 3,287,156; and 3,266,920.